N2 is a traditional cultural medium for OLs and NBM for neurons. When tested individually, they showed poor support for myelin formation. Interestingly, the combination of these two medium produced robust myelination. At present, the precise mechanism for the synergetic

effect of N2+ NBM on myelination remains unclear, but it appears that such combination leads to a well-balanced growth and differentiation of neurons and OLs. Furthermore, Inhibitors,research,lifescience,medical the OL developmental profile, that is, process extension, rather than the cell number, was noticeably enhanced. In contrast, the neurite density was only moderately improved (Fig. 1). It has been shown previously that process extension is an important step for premyelinating OLs to initially survey the local environment and locate suitable axons (Kirby et al. 2006). The high concentration of insulin Inhibitors,research,lifescience,medical in N2 has been shown to activate Akt-mediated survival pathways through the IGF-1 receptor, which is known to promote OL survival and proliferation (D’Ercole et al. 1996; Ebner et al. 2000). In contrast, NBM is known

for its antioxidative activity and thus may prevent cell degeneration (Xie et al. 1999). The combination of these Inhibitors,research,lifescience,medical two factors may enhance the initial survival and differentiation of neuron stem cells as well as the late specified neurons and OLs. After DIV10, cells survived and myelinated very well in the medium with a lower concentration of insulin (although N2 was insulin free, NBM still contains insulin). The PRT062607 price probable explanation is that neurons

and glia mutually support each other, since it is well known that both of them can secrete all those factors (Du and Dreyfus 2002; Althaus et al. 2008; Ndubaku and de Bellard 2008). Additionally, Inhibitors,research,lifescience,medical those secreted Inhibitors,research,lifescience,medical factors have also been suggested to support myelination by affecting OL differentiation (Simons and Trajkovic 2006; Xiao et al. 2009). Taken together, our defined medium is optimal to support neuronal and glial differentiation, resulting in extensive myelination that can be maintained at high levels without any obvious sign of degeneration after long-term culture (~three months). An interesting finding in this study is that the mechanism of myelination appears to differ in cultures derived from medroxyprogesterone the spinal cord versus cerebral cortex. The failure of myelination in the cortex-derived culture may be due to arrest in OL differentiation, since accelerating OL maturation by T3 resulted in a high level of myelination. The striking difference of OL development in these two CNS-derived cultures may be due to the intrinsic difference in OL differentiating potential, and/or differences in extrinsic factors produced by neurons and glia. Recent studies, for example, have suggested that OL differentiation is regulated by both an intrinsic clock that turns on in OL progenitor cells after certain divisions, and also by extrinsic cues provided by neighboring neurons and glia (Emery 2010).